1. Field
The present disclosure relates generally to communications systems and in particular to a method and apparatus for managing communications between data processing systems. Still more particularly, the present disclosure relates to a method, apparatus, and computer program code for managing directional network links in a communications system.
2. Background
Internet protocols were originally designed for what is referred to as the “wired” Internet. In this environment, physical links exist between routers and other devices in this type of network. Few decisions are to be made about the topology for this type of network except for the original setup or design of these links.
More recently, protocol development has moved to the direction of omni directional wireless networks. In order for a receiver to quickly decode a packet with this type of network, only one transmitter can use a particular frequency and code at a time within the transmission range of the receiver for omni directional wireless networks. Transmission power is limited to allow simultaneous transmissions to increase spatial reuse and minimize power consumption. The transmission power also is limited to reduce the impact on reception of other messages by other nodes.
This type of situation limits the number of neighboring nodes to a relatively small subset of the entire network. Increasing the number of neighbor nodes may unacceptably reduce the capacity of the network. A neighbor node is a node that is capable of directly communicating with the selected node in the network.
Additionally, with this type of network, nodes listen for communication omni directionally. This situation makes it relatively easy to reach nodes to coordinate a communication time. As a result, every node within this type of network is able to directly communicate with any other node in the neighborhood.
When nodes within the network use directional antennas, the situation may change. These directional antennas are typically high gain antennas. A high gain antenna may be chosen with characteristics, such as long communication range, high data rate, anti-jamming features, and low probability of detection.
These types of antennas also minimize interference with other transmissions or communications in the network. The gain is maximized when both the transmitter and receiver direct their antenna beams at each other. This type of directionality reduces interference because the transmissions between a transmitter and receiver may no longer interfere with nodes outside of the transmitter's beam.
In tactical applications, communication ranges of hundreds of kilometers may be achievable. These types of applications may results in hundreds or thousands of nodes being reachable. Forming a link with the different potential neighbor nodes may have a number of different costs.
For example, to effectively aim narrow transmit and receive beams, frequent exchanges of position information between the nodes may be required. These exchanges may reduce the throughput available for communications between the nodes. Further, if the time schedule is quantized into relatively large slots to allow the abstraction of variable signal time of flight, then allocating a large slot to links that have little or no data flow may result in a waste of resources in the network.
Further, with the use of conventional link-state routing protocols, a regular reporting of the existence of links is made to the rest of the network. If each node has many links, the overhead associated with this type of reporting may be unduly burdensome with respect to network resources. If only a few links are actually handling traffic, scheduling unnecessary transmissions also may increase the delay in transmitting data. This situation may result in an increase in the per-hop latency within the network.
Further, with many transmissions in various directions, interference may occur with respect to third parties that are not part of the communications. This type of interference may increase with long range and/or high power transmissions and may reduce the resources available to carry data within a network.